Turbidity-causing components can be any organic or inorganic species of sufficient particle or droplet size to create a turbid, light-dispersed appearance in waste waters, industrial waters, or natural waters. These turbidity-causing components can be of an inorganic nature, an organic nature, a color body, a pigment dispersion, an oil droplet, a colloidal humic material suspension, a dispersion formed from animal wastes in waters used to collect these animal wastes, sewage components, or admixtures of any of the above in any ratio in waters of any description thereby obtaining a turbid translucent effect.
Turbid waters are any type of waters having dispersed therein any type of turbidity-causing component, as described above, or any other type of turbidity-causing component which might be similar in effect when dispersed in these types of waters. For example, colloidal matter of either organic or inorganic or even mixed organic and inorganic character can be turbidity-causing. Such components may vary greatly in nature and concentration, but generally contain a highly anionic surface charge which causes the colloidal particles to repel one another, thus remaining dispersed in the water, rather than settling out in a reasonable time frame.
Examples of turbid waters include waste waters expelled from hydrocarbon processing plants, waste waters expelled from chemical processing plants which synthesize various types of rubber latexes, and effluent waters expelled from various kinds of processing plants using materials containing emulsified components which are of a hydrocarbon nature. Further, the waste waters may be from automotive plants or machining plant operations.
A common method for removal of suspended solids from various types of turbid waters is by the well-known chemical process of clarification. The primary unit operations in clarification are coagulation combined with or followed by flocculation. Coagulation is defined as neutralization of the surface charge on particles or droplets dispersed in the water. Flocculation is defined as the agglomeration or coalescence of small particles or droplets into larger particles or droplets, generally called floc.
A method of clarification usually comprises addition to the aqueous solution to be treated of certain chemicals known as coagulants, mixing of chemical additive and aqueous liquid whereby floc formation occurs, and subsequent removal of this floc by a variety of methods. In some cases, the addition of a second higher molecular weight water-soluble polymer, generally known as a flocculant may aid in the formation of floc. The removal of floc may be achieved by mechanical separation means or by merely allowing forces of gravity to work upon the agglomerated solids whereby a removable sludge layer is created.
Among effective coagulants for this purpose are water-soluble cationic polymers. These materials function by neutralizing the charge on the surface of the dispersed particles or droplets which allow the turbidity-causing materials present in turbid waters to agglomerate or coalesce, and to settle, or float to the top of the aqueous medium where they are collected and removed by techniques familiar to the those skilled in the art.
Water-soluble cationic polymers in conjunction with polynuclear aluminum species for clarifying waters containing turbidity-causing components are disclosed in U.S. Pat. No. 4,655,934. The reaction products of phenol, formaldehyde and low molecular weight polyamines useful for removing turbidity from low turbidity industrial waste waters are disclosed in U.S. Pat. No. 4,308,149.
Combinations of silica and polymers have been disclosed for some applications. The use of polymeric coagulants and aqueous colloidal silica sol for paint detackification is disclosed in U.S. Pat. Nos. 4,863,615; 5,004,550 and 4,153,548. A treatment of cationic coagulant, flocculant and colloidal silica was found to enhance the dewatering of paper in U.S. Pat. No. 4,795,531. However, none of these patents disclose methods for the reduction of turbidity, or compositions of colloidal silica blended with cationic polymers.